In recent years, improved fineness of patterns formed on semiconductor devices has led to shorter wavelengths of exposure light used for photolithography, i.e., ArF excimer laser (exposure wavelength of 193 nm), and F2 excimer laser (exposure wavelength of 157 nm). With regard to exposure masks used for the photolithography, and mask blanks used for manufacturing the exposure masks, there has been rapid development for opaque films for shielding the above-mentioned exposure wavelengths of exposure light and phase shift films for phase shift thereof, which are formed on transparent substrates for mask blanks (e.g., glass substrates), and various film materials have been proposed.
Also, exposure devices used in photolithography (e.g., steppers) have optical components such as lenses and the like, and materials with little absorption of exposure light, i.e., materials with good optical transparency are used for the optical components.
It is demanded of the mask blank transparent substrates and transparent articles for manufacturing the mask blank transparent substrates (e.g., synthetic quartz glass substrates) and optical components such as lenses and the like used in the exposure devices, that there be no optical inhomogeneity therein (change in optical properties due to defects such as foreign matter, bubbles, and so forth). Patent Document 1 discloses a detect detecting device and detect inspection method for detecting such optical inhomogeneity by irradiating a He—Ne laser into a glass substrate and detecting scattered light scattered by optical uniformity present within the glass substrate, e.g., the interior defects (foreign matter, bubbles, and so forth), thereby detecting the aforementioned optical uniformity.
Patent Document 1: Japanese Unexamined Patent Application Publication (JP-A) No. 8-261953
Patent Document 2: Japanese Unexamined Patent Application Publication (JP-A) No. 8-31723
Patent Document 3: Japanese Unexamined Patent Application Publication (JP-A) No. 2003-81654